Internet Engineering Task Force (IETF) A. Malis, Ed.
Request for Comments: 7709 Huawei Technologies
Category: Informational B. Wilson
ISSN: 2070-1721 Applied Communication Sciences
G. Clapp
AT&T Labs Research
V. Shukla
Verizon Communications
November 2015
Requirements for Very Fast Setup of GMPLS Label Switched Paths (LSPs)
Abstract
Establishment and control of Label Switch Paths (LSPs) have become
mainstream tools of commercial and government network providers. One
of the elements of further evolving such networks is scaling their
performance in terms of LSP bandwidth and traffic loads, LSP
intensity (e.g., rate of LSP creation, deletion, and modification),
LSP set up delay, quality-of-service differentiation, and different
levels of resilience.
The goal of this document is to present target scaling objectives and
the related protocol requirements for Generalized Multi-Protocol
Label Switching (GMPLS).
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7709.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Driving Applications and Their Requirements . . . . . . . . . 5
4.1. Key Application Requirements . . . . . . . . . . . . . . 5
5. Requirements for Very Fast Setup of GMPLS LSPs . . . . . . . 6
5.1. Protocol and Procedure Requirements . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Generalized Multi-Protocol Label Switching (GMPLS) [RFC3471]
[RFC3945] includes an architecture and a set of control-plane
protocols that can be used to operate data networks ranging from
packet-switch-capable networks, through those networks that use Time
Division Multiplexing, to WDM networks. The Path Computation Element
(PCE) architecture [RFC4655] defines functional components that can
be used to compute and suggest appropriate paths in connection-
oriented traffic-engineered networks. Additional wavelength switched
optical networks (WSON) considerations were defined in [RFC6163].
This document refers to the same general framework and technologies,
but it adds requirements related to expediting LSP setup under heavy
connection churn scenarios, while achieving low blocking under an
overall distributed control plane. This document focuses on a
specific problem space -- high-capacity and highly dynamic connection
request scenarios -- that may require clarification and or extensions
to current GMPLS protocols and procedures. In particular, the
purpose of this document is to address the potential need for
protocols and procedures that enable expediting the setup of LSPs in
high-churn scenarios. Both single-domain and multi-domain network
scenarios are considered.
This document focuses on the following two topics: 1) the driving
applications and main characteristics and requirements of this
problem space, and 2) the key requirements that may be novel with
respect to current GMPLS protocols.
This document presents the objectives and related requirements for
GMPLS to provide the control for networks operating with such
performance requirements. While specific deployment scenarios are
considered part of the presentation of objectives, the stated
requirements are aimed at ensuring the control protocols are not the
limiting factor in achieving a particular network's performance.
Implementation dependencies are out of scope of this document.
Other documents may be needed to define how GMPLS protocols meet the
requirements laid out in this document. Such future documents may
define extensions or simply clarify how existing mechanisms may be
used to address the key requirements of highly dynamic networks.
2. Background
The Defense Advanced Research Projects Agency (DARPA) Core Optical
Networks (CORONET) program [Chiu] is an example target environment
that includes IP and optical commercial and government networks, with
a focus on highly dynamic and resilient multi-terabit core networks.
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It anticipates the need for rapid (sub-second) setup and SONET/SDH-
like restoration times for high-churn (up to tens of requests per
second network wide and holding times as short as one second) on-
demand wavelength, sub-wavelength, and packet services for a variety
of applications (e.g., grid computing, cloud computing, data
visualization, fast data transfer, etc.). This must be done while
meeting stringent call-blocking requirements and while minimizing the
use of resources such as time slots, switch ports, wavelength
conversion, etc.
3. Motivation
The motivation for this document, and envisioned related future
documents, is two-fold:
1. The anticipated need for rapid setup, while maintaining low
blocking, of large bandwidth and highly churned on-demand
connections (in the form of sub-wavelengths, e.g., OTN ODUx, and
wavelengths, e.g., OTN OCh) for a variety of applications
including grid computing, cloud computing, data visualization,
and intra- and inter-datacenter communications.
2. The ability to set up circuit-like LSPs for large bandwidth flows
with low setup delays provides an alternative to packet-based
solutions implemented over static circuits that may require tying
up more expensive and power-consuming resources (e.g., router
ports). Reducing the LSP setup delay will reduce the minimum
bandwidth threshold at which a GMPLS circuit approach is
preferred over a layer 3 (e.g., IP) approach. Dynamic circuit
and virtual circuit switching intrinsically provide guaranteed
bandwidth, guaranteed low-latency and jitter, and faster
restoration, all of which are very hard to provide in packet-only
networks. Again, a key element in achieving these benefits is
enabling the fastest possible circuit setup times.
Future applications are expected to require setup times that are as
fast as 100 ms in highly dynamic, national-scale network environments
while meeting stringent blocking requirements and minimizing the use
of resources such as switch ports, wavelength converters/
regenerators, and other network design parameters. Of course, the
benefits of low setup delay diminish for connections with long
holding times. For some specific applications, a trade-off may be
required, as the need for rapid setup may be more important than
their requirements for other features currently provided in GMPLS
(e.g., robustness against setup errors).
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With the advent of data centers, cloud computing, video, gaming,
mobile and other broadband applications, it is anticipated that
connection request rates may increase, even for connections with
longer holding times, either during limited time periods (such as
during the restoration from a data center failure) or over the longer
term, to the point where the current GMPLS procedures of path
computation/selection and resource allocation may not be timely, thus
leading to increased blocking or increased resource cost. Thus,
extensions of GMPLS signaling and routing protocols (e.g., OSPF-TE)
may also be needed to address heavy churn of connection requests
(i.e., high-connection-request arrival rate) in networks with high-
traffic loads, even for connections with relatively longer holding
times.
4. Driving Applications and Their Requirements
There are several emerging applications that fall under the problem
space addressed here in several service areas such as provided by
telecommunication carriers, government networks, enterprise networks,
content providers, and cloud providers. Such applications include
research and education networks / grid computing, and cloud
computing. Detailing and standardizing protocols to address these
applications will expedite the transition to commercial deployment.
In the target environment, there are multiple Bandwidth-on-Demand
service requests per second, such as might arise as cloud services
proliferate. It includes dynamic services with connection setup
requirements that range from seconds to milliseconds. The aggregate
traffic demand, which is composed of both packet (IP) and circuit
(wavelength and sub-wavelength) services, represents a five to
twenty-fold increase over today's traffic levels for the largest of
any individual carrier. Thus, the aggressive requirements must be
met with solutions that are scalable, cost effective, and power
efficient, while providing the desired quality of service (QoS).
4.1. Key Application Requirements
There are two key performance-scaling requirements in the target
environment that are the main drivers behind this document:
1. Connection request rates ranging from a few requests per second
for high-capacity (e.g., 40 Gb/s, 100 Gb/s) wavelength-based LSPs
to around 100 requests per second for sub-wavelength LSPs (e.g.,
OTN ODU0, ODU1, and ODU2).
2. Connection setup delay of around 100 ms across a national or
regional network. To meet this target, assuming pipelined cross-
connection and worst-case propagation delay and hop count, it is
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estimated that the maximum processing delay per hop is around 700
microseconds [Lehmen]. Optimal path selection and resource
allocation may require somewhat longer processing (up to 5
milliseconds) in either the destination or source nodes and
possibly tighter processing delays (around 500 microseconds) in
intermediate nodes.
The model for a national network is that of the continental US with
up to 100 nodes and LSPs with distances up to ~3000 km and up to 15
hops.
A connection setup delay is defined here as the time between the
arrival of a connection request at an ingress edge switch -- or more
generally a Label Switch Router (LSR) -- and the time at which
information can start flowing from that ingress switch over that
connection. Note that this definition is more inclusive than the LSP
setup time defined in [RFC5814] and [RFC6777], which do not include
PCE path computation delays.
5. Requirements for Very Fast Setup of GMPLS LSPs
This section lists the protocol requirements for very fast setup of
GMPLS LSPs in order to adequately support the service characteristics
described in the previous sections. These requirements may be the
basis for future documents, some of which may be simply
informational, while others may describe specific GMPLS protocol
extensions. While some of these requirements may have implications
on implementations, the intent is for the requirements to apply to
GMPLS protocols and their standardized mechanisms.
5.1. Protocol and Procedure Requirements
R1 The portion of the LSP establishment time related to protocol
processing should scale linearly based on the number of traversed
nodes.
R2 End-to-end LSP data path availability should be bounded by the
worst-case single-node data path establishment time. In other
words, pipelined cross-connect processing as discussed in
[RFC6383] should be enabled.
R3 LSP establishment time shall depend on the number of nodes
supporting an LSP and link propagation delays and not on any off
(control) path transactions, e.g., PCC-PCE and PCC-PCC
communications at the time of connection setup, even when PCE-
based approaches are used.
R4 LSP holding times as short as one second must be supported.
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R5 The protocol aspects of LSP signaling must not preclude LSP
request rates of tens per second.
R6 The above requirements should be met even when there are failures
in connection establishment, i.e., LSPs should be established
faster than when crank-back is used.
R7 These requirements are applicable even when an LSP crosses one or
more administrative domains/boundaries.
R8 The above are additional requirements and do not replace existing
requirements, e.g., alarm-free setup and teardown, recovery, or
inter-domain confidentiality.
6. Security Considerations
Being able to support very fast setup and a high-churn rate of GMPLS
LSPs is not expected to adversely affect the underlying security
issues associated with existing GMPLS signaling. If encryption that
requires key exchange is intended to be used on the signaled LSPs,
then this requirement needs to be included as a part of the protocol
design process, as the usual extra round-trip time (RTT) for key
exchange will have an effect on the setup and churn rate of the GMPLS
LSPs. It is possible to amortize the costs of key exchange over
multiple exchanges (if those occur between the same peers) so that
some exchanges need not cost a full RTT and operate in so-called
zero-RTT mode.
7. Acknowledgements
The authors would like to thank Ann Von Lehmen, Joe Gannett, Ron
Skoog, and Haim Kobrinski of Applied Communication Sciences for their
comments and assistance on this document. Lou Berger provided
editorial comments on this document.
8. References
8.1. Normative References
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, DOI 10.17487/RFC3471, January 2003,
.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
DOI 10.17487/RFC3945, October 2004,
.
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RFC 7709 Very Fast Setup of GMPLS LSPs November 2015
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
.
[RFC5814] Sun, W., Ed. and G. Zhang, Ed., "Label Switched Path (LSP)
Dynamic Provisioning Performance Metrics in Generalized
MPLS Networks", RFC 5814, DOI 10.17487/RFC5814, March
2010, .
[RFC6163] Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
"Framework for GMPLS and Path Computation Element (PCE)
Control of Wavelength Switched Optical Networks (WSONs)",
RFC 6163, DOI 10.17487/RFC6163, April 2011,
.
[RFC6383] Shiomoto, K. and A. Farrel, "Advice on When It Is Safe to
Start Sending Data on Label Switched Paths Established
Using RSVP-TE", RFC 6383, DOI 10.17487/RFC6383, September
2011, .
[RFC6777] Sun, W., Ed., Zhang, G., Ed., Gao, J., Xie, G., and R.
Papneja, "Label Switched Path (LSP) Data Path Delay
Metrics in Generalized MPLS and MPLS Traffic Engineering
(MPLS-TE) Networks", RFC 6777, DOI 10.17487/RFC6777,
November 2012, .
8.2. Informative References
[Chiu] Chiu, A., et al., "Architectures and Protocols for
Capacity Efficient, Highly Dynamic and Highly Resilient
Core Networks", Journal of Optical Communications and
Networking vol. 4, No. 1, pp. 1-14, 2012,
DOI 10.1364/JOCN.4.000001,
.
[Lehmen] Von Lehmen, A., et al., "CORONET: Testbeds, Demonstration,
and Lessons Learned", Journal of Optical Communications
and Networking Vol. 7, Issue 3, pp. A447-A458, 2015,
DOI 10.1364/JOCN.7.00A447,
.
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Authors' Addresses
Andrew G. Malis (editor)
Huawei Technologies
Email: agmalis@gmail.com
Brian J. Wilson
Applied Communication Sciences
Email: bwilson@appcomsci.com
George Clapp
AT&T Labs Research
Email: clapp@research.att.com
Vishnu Shukla
Verizon Communications
Email: vishnu.shukla@verizon.com
Malis, et al. Informational [Page 9]